Social media music service Rdio recently landed $17.5 million in funding from Mangrove Capital Partners and Zennstrom's fund Atomico, as well as adding Warner Bros Records Chairman Rob Cavallo to their board.

As interesting as a big number like $17.5 million sounds, you have to ask -- is this for major Rdio expansion, or just investment because Rdio can't cover their operating costs? Investment rounds happen largely because of one or the other, and the reasons leading up to each are wholly different in the vitality of a company. It's worth asking why Rdio doesn't have the capacity to cover the expansion themselves, and finds it necessary to raise cash money from the venture capitalist scene. A Rdio spokesperson was not available for comment on Monday.

In a press release, Rdio points out in kind of a bland statement that the money will go to "hiring new talent, expanding outreach efforts to consumers, and continuing to innovate on new ways to bring the social music experience to music lovers," which generally means more jobs, more marketing and new ideas. But this still doesn't shed light on the health of the company. And making it in the music streaming service world is tough ... go ask the people at Spotify, Pandora, or any other service making razor-thin profit margins.

“We are changing the way we find and listen to music. Anything and everything is instantly available from any computer and phone and easily shared with our friends. The days of expensive music downloads are coming to an end," said Rdio co-founder Janus Friis in a statement.

Rdio was developed by the creators of Kazaa and Skype, which are Janus Friis and Niklas Zennström. Rdio has licensing with all four major record labels and multiple indie labels, with social media tools to share music. Twitter and Facebook support is included. The music sharing allows users to listen to the music of of other users they follow.

Rdio runs at a cost of $9.99 for mobile and Web access, while Web access only will cost $4.99 per month. It will feature both streaming and offline listening. The Rdio name is a combination of the words radio and audio, pronounced r-dee-o.